In some wireless communication systems, such as broadband and WiMax-type communication systems, data may be transmitted to receiving stations in bursts. Due to the volatile nature of the communication channel, the burst size of the physical layer frames may have to be changed frequently to help ensure successful transmissions. As a result, a media access controller of a conventional transmitting station may have to reconstruct previously constructed data units to fit into either smaller or larger burst size frames. This reconstruction is very time sensitive and any delay may result in a lost transmission opportunity leading to in-efficient spectrum usage.